Current liquid vitamin formulations contain relatively low amounts of water. Such formulations suffer from poor taste or palatability and high osmolality. The water content in such formulations is low due to the putative instability of some vitamins such as vitamin D. Vitamin D.sub.2 has been shown to deteriorate in propylene glycol when diluted in water; however, it has been taught to be stable in corn oil, propylene glycol, and milk (Tractor Jitco, Inc.: Scientific literature reviews on generally recognized as safe (GRAS) food ingredients--Vitamin D, PB-234 901, U.S. Dept. Commerce, July 1974; W. Huber and O. W. Barlow, "Chemical and Biological Stability of Crystalline Vitamins D.sub.2 and D.sub.3 and Their Derivatives," J. Biol Chem., 149, 125-137, 1943).
It is taught in the art that vitamin D is slowly destroyed in an alkaline medium or in the presence of light and air, and that it is stable at a mid-pH (M. Rechcigl, Jr., Ed., Handbook of Nutritive Value of Processed Food, Vol. I, "Food for Human Use," CRC Series in Nutrition and Food, 1982). It has also been disclosed that vitamin D is unstable in the presence of minerals (U.S. Pat. No. 2,758,923) and in an aqueous environment (D. R. Fraser and E. Kodicek, "Enzyme Studies on the Esterification of Vitamin D in Rat Tissues," Biochem. J. 109, 457 -467, 1968).
Liquid vitamin formulations currently commercially available include Poly-Vi-Sol.RTM. available from Mead Johnson Nutritionals, Evansville, Ind., U.S.A., and Polyvitamin Drops available from Rugby Laboratories. Increasing the water content will typically result in marked instability of vitamin D upon storage. Although the palatability of such a formulation is markedly improved with increased water content, the instability of vitamin D renders such a formulation commercially unfeasible. This problem has been solved by the present invention through the use of an ester of vitamin D.